Rare Sites of the Hydatid Cyst Mohammed Tafash Dagash

FICMS – CTVS , Instructor , Department of Surgery Al-Anbar Medical College.

Abstract: Background: Cystic hydatidosis caused by Echinococcus granulosus is an important zoonotic

world wide. Although all the sites of the body can be a possible location of the parasite , skin is an

example of an uncommon site.

Objective : To determine the hydatid cyst which can occur any where in human body even the skin

, & can deal with it first due to can do this operation under local anesthesia or possibility of rupture .

Materials& Methods: prospective study of five patients present with skin swelling . The diagnoses

were made in three cases by incidental finding during operation for exploration of the skin swelling

for diagnostic & therapeutic . The remaining two cases diagnosis is preoperative by high

suspension .

Results: out of five patients aged between 30-70 years with skin swelling (average 50 years ) , three

of them incidental discover preoperative with 60 % female & 40 % male .

Conclusion & Recommendation : Two of them are as secondary hydatid cyst & other three are

primary hydatid cyst . Although it is rare hydatid cyst of skin , it should be considered in the

differential diagnosis of skin swelling ,especially in endemic areas.

Key words : Hydatid cyst , Skin , Iraq .

Introduction : Hydatidosis caused by Echinococcus

granulosus is one of the most important

zoonotic disease. The four species known to

infect man are E.granulosus,E.multiloculosus,

E.oligrathrus , & E.vogeli. 1 Life cycle of the

parasite :

Fig. 1 Life cycle of the parasite 2

2

Hydatid disease is caused by the

adult & larval stages of Echinococcus

granulosus . The adult is a cestode of 5 to 7

mm in length with a scolex bearing four

suckers & with a body containing two to six

proglottids . The larval stage or metacestode

is a cyst with an acellular laminated outer

layer & an inner nucleated germinal layer

which gives rise to brood capsules & then

scolices.The adult worm lives in dog which

is the primary host. The cystic part of

the cycle occurs in sheep ,ox ,pig ,horse

camel or man , which act as intermediate

hosts.

The adult worm lives in the dog's intestine

for months. The terminal segment

proglottids detach from the worm & release

thousands of ova with the stools.

These are ovoid in shape & can remain

infective for long periods . ingestion of the

ova by sheep in contaminated water, grass

or vegetables causes infection ,& hydatid

cysts subsequently develop in the viscera

.The parasite gets back into the dog when

the sheep is slaughtered & its viscera

containing cysts are eaten by another dog.

In each of these cysts thousands of scolices

are found which will grow into new tape

worms in the dog,s intestine & so the cycle

repeats itself indefinitely.

If an ovum gets into a man instead of a

sheep, the life cycle of the parasite will be

broken, because the entrails of men are not

eaten by dogs.

Contamination of food is a common

source of infection in man ,more frequently

he contaminates his fingers by fondling a

dog & then takes his food without washing

his hands. The ova hatch in the stomach &

the hexacanth embryos or oncospheres are

released in the stomach & duodenum &

pass through the wall & travel via portal

vein to the liver , where the majority settle

& develop into hydatid cysts .

Only those embryos which

successfully pass through the capillaries in

the liver to reach the lungs develop into

hydatid cysts ,& few which get through the

lungs are then carried to the viscera &

tissues supplied by the systemic circulation .

Sometimes the hatched embryo passes

through the wall of the stomach or the

duodenum into a lymphatic channel to be

carried to the lungs via thoracic duct, thus

bypassing the liver , this explains the few

cases of pulmonary hydatids without

hepatic involvement . Once implanted in the

interstitial tissue of the lung, the embryo

grows into a vesicle & then into a hydatid

cyst. 3

The hydatid cyst is surrounded by a

capsule ,its adventitia ( pericyst ) is part of

the host , the hydatid cyst itself is composed

of a nucleated thin germinal layer

(endocyst) which secrets the hydatid fluid

into its cavity & forms externally an

acellular white laminated membrane

( ectocyst ). 3

A primary hydatid cyst indicates that

the cyst has developed from an

ovum,whilest secondary hydatid cyst means

that a primary cyst lodged in the lung , liver

or other site of the body has ruptured &

caused new daughter cysts to develop. 3

Materials & methods: This is a descriptive & prospective

study was done on 5 patients operated in

Al-Falluja General Hospital in the period of

July 2007- July 2008.

The collected data included age ,gender

,date of admission ,duration of swelling

,history of contact with dogs & endemic

areas from the patients or from their

relatives.

Three cases from the periphery of city &

other from center of city with history of

traveling to rural area during the 3rd Gulf

war .

3

The diagnosis was made in different ways ,

group of patients ( 3 cases ) incidentally

discover during operative exploration of the

skin swelling for diagnostic & therapeutic .

Another group of patients ( 2 cases )

diagnosed preliminary by history of a know

case of hydatid cyst ,radiographic for chest ,

localize site ( upper third of left leg hydatid

cyst involving tibia & fibula) &

ultrasonography .

Cystectomy was performed under local

anesthesia in 2 patients & 3 patients under

general anesthesia .

The tissue & cyst obtained after operation

subjected to histopathlogical study in 4 cases

reveally hydatid cyst , other case by

macroscopical appearance ( case no.1) &

latter on by right thoracotomy for lung

hydatid cyst.

Results:

Age , gender,complain,duration,local sign,

type of anesthesia,diagnosis,other organ

involvement, type of hydatid cyst &

histopathological study distribution will be

shown in table 1,2 & 3 respectively.

Case no.

Age/ year

Gender

1.

30 y.

Female

2. 39 y.

Male

3.

70 y.

Female

4.

35 y.

Male

5. 55 y. Female

Table 1 : Distribution of cases according the age & gender.

4

Case

no.

Complain/ duration

Local sign

Other organ involve (liver

& lung)

1 Double cystic swelling on

right shoulder/ 1 year

Round mobile not

pulsatile mass

Liver & lung involve

(ultrasound & chest x-

ray)

2 Single cystic mass on the

back/ 1 year

Fluctuant

,painless, with

skin vascular

change

Not involve

3

Single left

supraclavicular mass / 5

year

Mobile cystic

mass, not

pulsatile

Not involve

4

Cystic lesion at the site of

previous thoracotomy

incision / 1 year

Mobile, cystic

mass, scar of

thoracotomy

before 10 year

Right lung & posterior

mediastinum

5

Recurrent cystic lesion

on left upper 3rd

of leg

just below knee/ 2 year

Mobile cystic

mass Not involve

Table 2 : distribution of cases according complain ,duration ,local sign & other organ involvement.

Case no.

Type of

anasthesia

Diagnosis

Type of hydatid

cyst

Histopatholog

1

Local

incidental

primary

Macroscopical features of

H.cyst

2

Local

incidental

primary

Macroscopical & microscopical

3

General

incidental

primary

Macroscopical & microscopical

4

General

High suspension with history of

lung Hydatid cyst

secondary

Macroscopical & microscopical

5

5

General

High suspension with a known

case in the same site

secondary

Macroscopical & microscopical

Table 3 : distribution of cases according type of anesthesia,diagnosis,type of hydatid cyst &

histopathological study.

A total number of 5 patients with skin hydatid cyst aged between 30-70 years ( mean age 50 years ).

Male :female ratio 2:3 .

Fig. 2 Gender distribution

Three patients diagnosed incidentally during operation & 2 diagnosed preoperatively .

The study also showed that 40% of male & 60% of female patients.

0%

10%

20%

30%

40%

50%

60%

70%

local

Anasth

general

Anesth

incidental

Descover .

akown

case

local anasthesia

general

anasthesia incidental

descover akown case

male 40%

female 60%

6

Fig.3 Type of anesthesia & diagnosis .

Fig.4 Type of cysts.

The interesting aspect of 3 cases ( case no.2 , 3 & 5 ) with solitary cysts in skin is the absence of

disease in the liver & lungs .

primary type 60 %

secondary type 40 %

7

Figure 5 case no. 1 before surgery Figure 6 case no.1 after surgery

Figure 8 : case no.2 after surgery Figure 7 : case no.2 before surgery.

8

Figure 9 : case no.3 before surgery Figure 10 : case no.3 after surgery

9

Figure 14 case no.5 tibia & fibula Figure 15 case no.5 during surgery.

Involvement with skin involved.

Figure 13 case no.4

after surgery.

Figure 11 case no.4 chest

x-ray lateral view

Figure 10 case no.4 before surgery

10

Discussion:

Hydatid disease is caused by Echinococcus granulosus. The adult parasite ,resides

in the intestine of animals such as dogs ,foxes ,jackals ( as definitive hosts ).

Hydatid disease exists all over the world (endemic in the great sheep-rearing

countries ) & it is a major health problem & serious public health hazard for the

community. In Iraq it is still hyperendemic & is considered to be one of the most

serious helmenthic diseases in the country. 4

The ova ,which are resistant to many environmental conditions ,are excreted in

the feces, & ingested by the intermediate hosts ,herbivores & humans .

The ova hatch in the small intestine ,where the parasite penetrate the mucosal wall

& reach the liver via the portal vein . The are trapped in the sinusoids, therefore ,the

liver is the most frequently involved organ ( 70%) 5.

The larva which passes through this first filter ,reaches the lung via the right heart,

the lung is the second most frequent involved site ( 10-15%). The larva, which passes

through this second filter causes hydatid disease in other organs ( 5-15%). 5

In large series from Greece, the frequency of extrahepatic & extrapulmonary

hydatidosis was 9% . 6

In our cases , the cyst was in the subcutaneous tissue in the shoulder, back of the

chest,supraclavicular region, chest wall & left lower limb respectively . In a different

series , the frequency of subcutaneous tissue involvement was approximately 2 % . 7

Most patients were within the age above 30 years ,this goes with the history of

infection in teenage & appears after years .

Gender distribution nearly is not different in ratio 2:3 male to female ,more in female

may be due to more contact with dogs in the periphery of city.

The interesting aspect of three cases ( case no.2,3 & 5 ) with subcutaneous cysts is

the absence of disease in the liver & lung . It is very difficult to explain how the

larvae pass through two filter sites & form subcutaneous tissue cysts. Although no

route other than the portal route has been proved in humans, it is strongly possible that

systemic dissemination via the lymphatic route accounts for cases with subcutaneous

tissue cysts in rare sites.

In the other 2 cases ( case no. 1 & 4 ) , with the history of hydatid cyst in other

organs ( liver, lung & bone ) recurrent it more than reinfestation

Diagnosis depends on the basis of the history ,radiology , ultrasound finding,

serological investigation & incidental discovery. In suspected mass fine needle

aspiration biopsy can reveal the early diagnosis by observing the hooklets of the

parasite. However, the fine needle aspiration should be avoided because of high risk

of anaphlactoid reaction & spillage in suspected lesions . 11

In our cases there were incidental discover of 3 case & high suspension in other

cases.

Upon surgical exploration, the mass was found to be attached to the subcutaneous

tissue. the macroscopic appearance suggested a hydatid cyst, perforation was avoided

by means of meticulous dissection .because the preoperative diagnosis had not been

hydatid disease in 3 cases ( no.1,2,& 3 ), investigation for other organ involvement (

including liver ultrasonography & chest x-ray ) was performed postoperatively & no

other focus was found in case no .2 & 3 ,while other focus found in case no.1 ( liver &

lung involvement .

11

Histopathologic examination of the specimen in cases no 2,3,4 & 5 revealed a

hydatid cyst .while in case no.1 macroscopic appearance as hydatid cyst & after 6

month through right thoracotomy for lung hydatid cyst confirm the diagnosis.

As in the other hydatid lesions of the body ,surgical removal without spillage is the

best method of treatment. 12

Local anesthesia in the 2 cases for diagnostic &

therapeutic intervention skin swelling .

Chemotherapy with mebendazole is of limited valve ,the most satisfactory treatment

is complete excision of the cyst together with its contained parasites. 9

In case no. 4 in addition to involvement of the subcutaneous of the chest wall ,the

other hydatid cyst present in the posterior mediastinum & right upper lobe of lung

In the case no.5 with involvement of fibula & tibia referral the patient to orthopedic

surgeon for complete treatment due to involvement of the bone. Complete cure of the

osseous involvement is a therapeutic challenge .The disease generally is not curable &

recurrence is likely. Surgery is the treatment of choice in osseous Echinococcus .

Although it can only eliminate the macroscopic cysts and local recurrence is reported

in half of patients , treatment should include a combination of surgery and

chemotherapy with albendazole.

Osseous hydatid disease behaves like a locally aggressive relapsing bone tumour.1

Skeletal tumour treatment strategies such as total excision with either biologic or

prostheticExtensive curettage and irrigation followed by filling the cavity with

massive allograft chips was performed . 13

cyst fluid is highly allergenic & spillage at surgery may precipitate a type I

anaphylactic hypersensitivily reaction . 8 &10

This is a phenomenon which was not

encountered in over 5 cases.

The most effective scolicidal agents are: 1.hypertonic saline 2.formalin

3.alcohol 4. 0.5 % silver nitrate solution 2 . In our cases they are not used, & replaced

by isolating the area of surgery by iodined packing & meticulous dissection.

Upon questioning the patient reported close contact with dogs for the last five years

in cases no. 1 ,3 & case no. 4.

Focuses on other organ involvement on liver & lung due to the most common site of

hydatid cyst

An uneventful course was noticed in this study ….No mortality ,with morbidity as

skin infection in case no.4 & 5.

The most important issue in cases with cysts in rare sites is whether hydatidosis

will develop in the primary sites. these patients should be followed, paying close

attention to this possibility .

Conclusion & Recommendation :

1. Hydatid cysts are still an incidental discovery.

2. CXR is still one of the important investigations .

3. It can occur any where in the body.

4. Hydatid disease should be considered in the differential diagnosis of any skin

swelling , especially in endemic areas (our country), since this diagnosis may easily

be missed unless kept in mind.

5. No drug that can cure the disease ,& surgical intervention is mandatory due to the

natural history of hydatid disease.

6. Prophylaxis is the logic approach in the measures including ; dog, sheep & man.

References:

12

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